Now and before.

[Nonpareil]

If someone standing beside me is suddenly shot, I don't have to find the shooter to know that there is a gun involved.

The shooter, gun and bullet all are seeable, touchable matter  that effect the outcome, dark matter has none of their qualities if it did we would have proof of it's existence.

It is at this point that I really have to pause the discussion and ask what you think the phrase "dark matter" means, and what you think our understanding of it is.

In brief, and very much simplified: our current understanding of gravity indicates that galaxies should behave in a certain way, assuming that mass is distributed throughout their structures as we would expect it to be. However, when we look at some galaxies, we see them behaving differently, which indicates one of two possibilities: either our understanding of gravity is completely wrong, or there is more matter in those galaxies than we can see. Since our understanding of gravity seems to work pretty well, all things considered, it doesn't look like the first is a real possibility, so we look at the second - there's more matter there, but we can't see it with our current limited tools - as the operational one, and the one worth the most investigation.

We call this stuff that we can't see "dark matter".

This is why I used the example of a person getting shot indicating the presence of a shooter. It wasn't an inaccurate analogy. When someone is shot, we can look at the wound and see the bullet. We know what fires bullets - guns - and so we can safely conclude that this person was shot by a gun.

In the same way, when we look at these galaxies and see them behaving as though there is a large gravitational force acting on them, we know that what causes gravitational forces is mass, and thus conclude that there must be some mass there, even though we can't directly see it.

Now, is it possible that our understanding of gravity is completely wrong? I would personally say that the chances of that are so low as to be effectively nil, but for the sake of this discussion, we can say that yes, it is a technical possibility. In the same way, it is technically possible that, if someone standing next to you was shot, there was, in fact, no shooter, but instead a freak spark of electricity or whatever set off an unprecedented magnetic storm, or whatever, and simply threw the bullet into the man's chest.

So yes. The theories concerning dark matter could be overturned at some point in the future. They are not yet one hundred percent established as fact. But they are still evidence-based, and are rational conclusions when working with the data that we have available. Belief in God is not evidence-based.

The comparison remains invalid.

I have evidence God exists

No, you don't.

The Bible has been used to discover many places lost to time and is still used today in that manner. That is evidence whether you think so or not.

No, it's not. Even if all of this were true - and it isn't, but I don't care to get into the discussion, because it is once again irrelevant - it would not in any way make the Bible evidence for the existence of a deity.